l-lysine (pH 6.0) induces germination of spores of Clostridium perfringens type F isolates carrying chromosomal or plasmid-borne enterotoxin gene

C. perfringens type F isolates carrying enterotoxin gene (cpe) on the chromosome (C-cpe isolates) are mostly associated with food poisoning, while isolates carrying plasmid-borne cpe (P-cpe isolates) with non-food-borne gastrointestinal diseases. Spore germination is considered the most essential step for initiation of these diseases. Identifying the most effective germinants for spores of C-cpe and P-cpe isolates should help developing novel strategies involving induction of spore germination followed by inactivation of germinated spores with mild treatments. In this study, we showed that (i) l-lysine (pH 6.0) triggered germination of spores of all tested C-cpe and P-cpe isolates; although extremely low concentration of l-lysine (5-10 mM) induced germination of C-cpe spores, 10-fold higher concentration (50 mM) was required for P-cpe spore germination; (ii) P-cpe strain F4969 gerKC spores did not germinate, C-cpe strain SM101 gerKC spores germinated extremely poorly and these gerKC spores released significantly less DPA as compared to wild type spores; and these defects were restored to a nearly wild-type level by complementing gerKC spores with wild-type gerKC; and (iii) F4969 gerAA spores also did not germinate, and released less DPA than wild-type spores in presence of l-lysine (pH 6.0); and these defects were restored partially (germination) and fully (DPA release) by complimenting gerAA spores with wild-type gerAA. Collectively, our current study identified l-lysine as a universal germinant for spores of both C-cpe and P-cpe isolates and provided evidence that GerKC (from SM101 or F4969) and F4969 GerAA play major roles in l-lysine-induced germination.